This invention relates generally to the attachment of handles to tools such as shovels, pitchforks or the like, and more particularly to a flexible core for insertion into a portion of the handle socket of such a tool to prevent the collapse of that portion during use of the tool.
Historically, most shovels and spades have been produced with a socket ranging from 6" to 24" long, projecting from the spade blade consisting of a sheath of metal, usually steel, wrapped around to form a conical socket into which a wood handle is inserted and fixed by means of rivets, screw, nails, collars, or the like. The primary reason for this traditional socket over many hundreds of years is that the traditional handle material has been wood and the projecting socket of metal was required to develop an attachment method that would generate adequate strength at the connection to allow the shovel handle made of wood to do its job plus resist collapse of the tubular socket adjacent to the blade when subjected to bending stress.
Depending on the difficulty of the operation, the length of the shovel handle, and the quality of the wood in the shovel handle, the socket was made longer or shorter. Further, in regard to the difficulty of the task to which the shovel was to be applied, the blade was produced either by stamping and forming metal sheet stock, or in very difficult operations, using a billet and forging a heavy duty blade. In virtually all operations whether the shovel blade was made from very thin metal for very low priced and light weight work, or forged from a billet, the handle socket was formed by rolling the sheet or forged stock into a conical section, and the conical section was prevented from opening up by means of either welding the edges together or bolting through the handle shaft stock so that the conical section could not spread out or open up when load was applied on the handle.
The sockets for the spade, shovels, forks, or the like usually are either a straight conical socket, that is straight from the opening which will accept the wood handle to the connection or attachment, or junction of the tool blade, or the socket was curved as it approached the smallest point of the socket section so as to create a desired angle between the plane of the blade and the axis of the shovel handle. Not all angles of different model shovels or for that matter, different makers, are the same, even though the traditional diameter of the shovel handle remains almost universal at about 11/2" at the entrance to the metal socket.
Using the traditional material--wood--for a handle, and turning a conical section on the end to be attached to the shovel to match the internal conical section of the blade socket, provided a secondary value in that the wood being a solid cross section and with acceptable compressive strengths could act as a filler the full length of the metal socket of the blade. This filler is necessary to resist a compressive failure of the metal conical section when the tool is used as a pry in either digging or actually prying. This failure will occur on every quality tool at a relatively low load level if a core is not inserted which has adequate compressive strength to prevent the collapse of the conical tubing section which has been created out of sheet stock or by forging.
Because the fiberglass shaft is produced from a thermosetting resin which is irreversible, that is, it cannot be softened by re-application of heat, it is not practical nor is it necessary to use the quality (and cost) of fiberglass to project into the socket of the tool blade where only compressive strength is needed. Moreover, it is particularly difficult and costly to attempt to machine, in some fashion, the fiberglass to be inserted in a socket which has an angle or curve as above described.
For handles originally fitted at the factory, wood can be so used as it can be autoclaved or steamed until malleable, and while malleable, driven into the socket at which time the wooden tip can be formed to fit the angled or curved section of the socket. On wood replacement handles, it is the practice to put one or more longitudinal slits in the handle at the socket end to allow the section to dry or cold form to a better degree into the curved sockets. This is not the best solution, but it is the best solution presently available.